Thanks to the recent quick development in the electronic industry, various kinds of electronic elements now have largely upgraded performance and constantly increased computing and data processing speed. In response to the constantly increased computing speed, the number of chips in the electronic elements also increases. The large number of chips produces more heat during operation thereof, and the produced heat must be timely removed or dissipated to avoid reverse influences on the electronic elements, such as lowered computing and data processing speed. Accumulated heat in the electronic elements would even burn out the electronic elements. Therefore, heat dissipation of electronic elements has already become a very important issue in the electronic industry. One of the most common ways for dissipating the heat produced by the electronic elements is the use of a cooling fan.
For example, when a computer operates, the central processing unit (CPU) thereof would produce a high amount of heat to have a raised temperature, which will cause an unstable state of the CPU and accordingly, a crashed computer or even a burned-out CPU. It is therefore very important for the cooling fan to quickly guide heat out of the CPU and other heat-producing electronic elements.
In view of the largely reduced thickness of currently designed computers, the cooling fan for dissipating heat from a slim-type computer must be able to guide airflow quickly and have a low profile. Since the overall height of a cooling fan has close relation with the heights of the fan's motor, circuit board and many other electronic elements, it is also very important in designing the fan's overall thickness.
FIG. 1 is a partial sectional view of a conventional cooling fan 1. As shown, the cooling fan 1 includes a seat 11 and a motor assembly 12. The seat 11 is provided with a forward projected hollow bearing cup 111 for receiving a bearing 112 therein. The motor assembly 12 is located around an outer side of the bearing cup 111, and includes a plurality of silicon steel plates 121, one or more insulating frames 122 and a circuit board 123. The silicon steel plates 121 and the insulating frames 122 are wound around by coils and are located on the circuit board 123. That is, the motor assembly 12 is mounted on the seat 11 via the circuit board 123. A space is left between the seat 11 and the circuit board 123 for accommodating a plurality of electronic elements 1231 of the circuit board 123. While the cooling fan 1 has a limited overall height, the motor assembly 12 has occupied a large part of an inner space of the cooling fan 1 and a space must be left between the circuit board 123 and the seat 11 for the electronic elements 1231. As a result, the remaining space in the cooling fan can only allow for a reduced number of silicon steel plates 121. However, with the reduced number of silicon steel plates 121, the motor assembly 12 would have lowered working efficiency and the cooling fan 1 would need increased electric current to operate.
In brief, the conventional cooling fan has the following disadvantages: (1) providing only limited space for stacking limited number of silicon steel plates in the motor assembly; (2) low motor working efficiency; and (3) increased electric current needed by the cooling fan to operate.
It is therefore tried by the inventor to develop an improved base structure for cooling fan, in order to overcome the disadvantages in the conventional cooling fan.